Voice filter system for a video camera

ABSTRACT

A one-piece type video camera comprises a device for taking the image of a subject, a device for collecting the voice and a device for magnetically recording the image and voice, all of which are built in the camera as one piece. The voice collecting device includes a microphone for collecting the voice incoming from the subject and another microphone for collecting the operator&#39;s voice. The operator&#39;s voice is subtracted from the voice incoming from the subject such that only the latter will be recorded. The operator&#39;s voice is utilized in the voice recognition technique so as to control the entire system of the video camera. In a preferred embodiment, the microphones are directional microphones.

This application is a divisional of application Ser. No. 08/300,520,filed on Sep. 6, 1994, which is a continuation of application Ser. No.08/099,407, filed on Jul. 30, 1993 now abandoned; which is acontinuation of application Ser. No. 07/727,003, filed on Jul. 8, 1991now abandoned, the entire contents of which are hereby incorporated byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention:

The present invention relates to a one-piece type video camera.

2. Description of the Related Arts:

FIG. 10 is a perspective view of a conventional one-piece type videocamera as viewed obliquely from a backward and upward position whileFIG. 11 is a perspective view of the same video camera as viewedobliquely from a forward and upward position. The video camera 10comprises a first microphone 1 for collecting sounds from a subject; azoom button 3; a grip belt 4; a stand-by switch 5; a start/stop button6; a view finder for monitoring a scene being shot; and a rear-lightcompensating switch 8.

When a change in the angle of view is desired in the conventional videocamera 10, an operator is required to move one finger in his hand placedwithin the grip belt 4 and holding the video camera 10 and to depressthe zoom button 3. The motion of the operator's finger may provide anundesirable motion in the video camera 10 itself.

If it is also wanted to take a subject placed before a source of light,the operator must manipulate the rear-light compensating switch 8 withhis hand other than the hand holding the camera 10. Since thisrear-light compensating switch 8 is disposed on the opposite side of thevideo camera 10 to its area held by the operator's hand, however, theoperator may look for the rear-light compensating switch 8 with hiseyes. This means that the operator's face is placed out of the viewfinder 7 so that the scene being shot will not be monitored by theoperator.

The operator's voice is collected by the microphone 1 and recorded on arecording tape. Particularly, if the sensitivity of the microphone 1 isincreased since the distance between the video camera and the subject islarge, the operator's voice will be recorded at an increased recordinglevel without properly recording the voice from the subject.

Furthermore, noises from the internal drive movers of the video camera10 such as capstan motor, rotary drum motor, zoom drive motor and othersalso are recorded. It is thus difficult to improve S/N ratio in voicesignals.

In order to prevent the video camera from being undesirably moved whenperforming zooming or the rear-light compensation, it may be desirableto control the video camera with generation of the operator's voice.However, this may raise another problem in that the operator's voicecommanding the operational mode to the video camera becomes offensive tothe ear on play-back.

SUMMARY OF THE INVENTION

In order to overcome such problems, an object of the present inventionis to provide an improved video camera which will not record theoperator's voice on a magnetic tape at such a level that the operator'svoice becomes any obstacle on play-back.

Another object of the present invention is to provide an improved videocamera which can prevent the video camera from being undesirably movedby controlling the operational mode of the video camera with theoperator's command voice and yet will not record the operator's commandvoice on a magnetic tape at such a level that the operator's commandvoice becomes any obstacle on play-back.

To this end, the present invention provides a video camera comprising:

A) a first microphone having a directivity toward an subject and adaptedto collect a voice incoming from the subject and to convert the voiceinto a first output voice signal;

B) a second microphone having a directivity toward an operator andadapted to collect a voice from the operator and to convert the voiceinto a second output voice signal;

C) subtractor means for subtracting the second output voice signal fromthe first output voice signal to form a differential output signal;

D) an optical system for taking the image of the subject; and

E) recording means for recording the differential signal and the image.

Such an arrangement can prevent the operator's voice from being recordedor reduce the operator's voice to such a level that it will not be anyobstacle to the ear.

The subtractor means may be consisted of an operational amplifier. Theoperational amplifier may take the first voice signal through itsnon-invert input terminal and the second voice signal through its invertinput terminal. Thus, the output of the operational amplifier will be anamplified signal representing a difference between the first and secondvoice signals. Such an amplified signal can be used as a differentialsignal. In other words, the generation of differential signal can berealized simply by any suitable parts currently used in the art.

It is also preferred to provide a switch for selecting either of thefirst or second voice signal to be supplied to the recording means. Thisalso permits for the operator's voice to be recorded. Thus, the videocamera is improved in utility.

In order to further improve the reduction of the level at which theoperator's voice is to be recorded, it is preferred to provide afrequency filter for causing the frequency characteristics and level ofthe second voice signal to match those of the first voice signal.

Considering time required to propagate the voice, still furtherimprovement of the reduction of the level at which the operator's voiceis to be recorded can be arraigned by providing a delay for compensatinga difference between time required to propagate the voice between thefirst microphone and the subject and time required to transmit the voicebetween the second microphone and the operator.

In addition, voice recognition may be adopted in the present invention.More particularly, the second microphone, which has been used to takethe voice to be cut out from the first voice signal, may be utilized tocontrol various sections in the video camera. In such a case, voicerecognizing means is used such that it judges whether or not the secondvoice signal is a given word. If the second voice signal is that word,the voice recognizing means outputs a mode command signal correspondingto the word. The mode command signal is applied to a controller whichcontrols the recording means and/or optical system depending on the modecommand signal.

It is further preferred that the second microphone also takes variousmechanical vibrations in the one-piece type video camera in addition tothe operator's voice. Thus, the adverse affection of the mechanicalvibrations to the recording operation can be reduced.

The present invention also provides a video camera comprising:

A) a first microphone having a directivity toward an subject and adaptedto collect a voice incoming from the subject and to convert the voiceinto a first output voice signal;

B) a second microphone having a directivity toward an operator andadapted to collect a voice from the operator and to convert the voiceinto a second output voice signal;

C) a first envelope detecting circuit for detecting the envelope of thefirst voice signal;

D) a second envelope detecting circuit for detecting the envelope of thesecond voice signal;

E) subtractor means for subtracting the output of the second envelopedetecting circuit from the output of the first envelope detectingcircuit to output a gain control signal;

F) a gain control circuit for controlling the level of the first voicesignal depending on the gain control signal;

G) an optical system for taking the image of the subject; and

H) recording means for recording, on a magnetic recording medium, thefirst voice signal and subject's image which have been controlled inlevel by the gain control circuit.

In such an arrangement, the subtractor means may be realized by ageneral circuit component which is an operational amplifier. Moreparticularly, if the non-invert input terminal of the subtractor meansreceives the output of the first envelope detector while the invertinput terminal thereof receives the output of the second envelopedetector, the output of the operational amplifier will be an amplifiedsignal representing a difference between the outputs of first and secondenvelope detecting circuits. This signal can be utilized as a gaincontrol signal.

In addition to the subtractor means, the gain control circuit may beconsisted of an operational amplifier which is adapted to take in andamplify the first voice signal. Further, the gain control circuit musthave a function which regulates the level of the first voice signal.Such a function can be attained by providing a feedback resistor whichis variable in resistance depending on the value of the gain controlsignal.

It is also preferred herein to provide a switch for selecting whether ornot the operator's voice is to be recorded. In such a case, however,this switch will have a function which causes the recording means toreceive the first voice signal either when it has passed through thegain control circuit or when the first voice signal has not passedthrough the gain control circuit.

In addition, this arrangement may include an additional operationcontrol function utilizing the voice recognition with respect to thesecond voice signal. This can be realized by the aforementionedarrangement.

The present invention further provides a one-piece type video cameracomprising:

A) an optical system for taking the image of a subject;

B) a first microphone having a directivity toward an subject and adaptedto collect a voice incoming from the subject and to convert the voiceinto a first output voice signal;

C) a second microphone having a directivity toward an operator andadapted to collect a voice from the operator and any mechanicalvibration in the one-piece type video camera and to convert the voiceand mechanical vibration into a second output voice signal;

D) a differential amplifier for subtracting the second voice signal fromthe first voice signal to output an amplified difference signal and alsofor summing the first and second voice signals to output an amplifiedsum signal;

E) recording means for recording the difference signal and image on amagnetic recording medium;

F) voice recognizing means for recognizing the sum signal to be voiceand for outputting a mode command signal corresponding to a given wordif said sum signal is said word; and

G) control means for controlling said recording means and said opticalsystem depending on the value of said mode command signal.

This arrangement is characterized by recording the difference signal andcontrolling the various operational sections in responsive to the sumsignal. The arrangement is optimized according to the basic concept ofthe present invention such that any undesirable noises such as theoperator's voice and other noises can be eliminated from voice signalsto be recorded and also the one-piece type video camera can bemanipulated and used more simply and easily by utilizing the voicerecognition. Therefore, the functions and advantages of the presentinvention can be accomplished by this more simplified arrangement.

The voice recognizing system may be realized as follows:

The voice recognizing system comprises a plurality of analog datagenerator means each of which filtrates and rectifies a sum signal togenerate a channel of analog data. The channels of analog data are thenmultiplexed by a multiplexer. The multiplexed analog data are convertedinto digital data by an analog/digital converter. Subsequently, areference is made to a dictionary data storage section by amicrocomputer. The dictionary data storage section stores preselectedwords. Thus, this reference can obtain information of a necessary wordwhich has been stored in the dictionary data storage section. Themicrocomputer judges whether or not the digital data is-agree with anyone of the words which have been stored in the dictionary data storagesection. If the digital data is agree with one of these words, themicrocomputer outputs a mode command signal representing that word.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a circuit diagram of the first embodiment of a one-piece typevideo camera constructed in accordance with the present invention.

FIG. 2 is a perspective view of the external form of the video cameraaccording to the first embodiment of the present invention.

FIG. 3 is a circuit diagram of the second embodiment of a one-piece typevideo camera constructed in accordance with the present invention.

FIG. 4 is a circuit diagram of the third embodiment of a one-piece typevideo camera constructed in accordance with the present invention.

FIG. 5 is a circuit diagram of the fourth embodiment of a one-piece typevideo camera constructed in accordance with the present invention.

FIG. 6 is a circuit diagram of the fifth embodiment of a one-piece typevideo camera constructed in accordance with the present invention.

FIG. 7 is a circuit diagram of the sixth embodiment of a one-piece typevideo camera constructed in accordance with the present invention.

FIG. 8 is a circuit diagram of the seventh embodiment of a one-piecetype video camera constructed in accordance with the present invention.

FIG. 9 is a view illustrating the arrangement and operation of the voicerecognizing system used in the seventh embodiment.

FIG. 10 is a perspective view illustrating the external form of aone-piece type video camera according to the prior art.

FIG. 11 is a perspective view illustrating the external form of anotherone-piece type video camera according to the prior art.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIGS. 1 and 2, there is shown a video camera 110 comprisinga second microphone 102 which is a narrow-beamed microphone so locatedthat it will be positioned adjacent to the mouth of an operator when helooks in a finder 107. The video camera 110 also comprises a frequencyfilter 150 having a filter characteristic which is set such that afterthe operator's voice signal collected through the second microphone 102has passed through the frequency filter 150, the frequencycharacteristic and level of that operator's voice signal will be equalto those of the operator's voice signal collected through a firstmicrophone 101. The characteristics of the frequency filter 150 dependson various factors such that the structure of the video camera 110itself, the directivities of the first and second microphones 101, 102and others.

The video camera 110 further comprises an operational amplifier 120which is adapted to subtract the output voice signal of the frequencyfilter 150 from the voice signal collected through the first microphone101. Thus, the output voice signal of the operational amplifier 120 willbe a new voice signal having a difference component in which theoperator's voice is reduced. Thus, the new voice signal will not berecorded at such a level that it becomes an obstacle to the ear onplay-back.

The video camera further comprises a switch 109 for selecting one of theoutput voice signals of the operational amplifier 120 and firstmicrophone 101, which is to be applied to a recording section 111. Byoperating this switch 109, therefore, the operator's voice can be cutoff optionally.

In accordance with the first embodiment, the operator's voice will notbe substantially recorded when the switch 109 is shifted to connect witha terminal a. On the other hand, if the switch 109 is on the otherterminal b, the operator's voice can be recorded by the recorder 111.

FIG. 3 shows a block diagram of an internal circuit used in the secondembodiment of the present invention, which circuit is similar to that ofthe first embodiment except that a delay element 245 is added betweenthe second microphone 202 and the frequency filter 250. The delayelement 245 is adapted to compensate a time delay between the operator'svoice signals respectively collected through the first and secondmicrophones 201, 202. The time delay depends on the positionalrelationship between the first and second microphones 201, 202. Thedelay element may be of any suitable configuration such as BBD (bucketbrigade device), CCD (charge coupled device), glass delay line or thelike.

Referring to FIG. 4, there is shown a circuit which is used in the thirdembodiment of a video camera constructed according to the presentinvention. Such a circuit comprises two envelope detectors 346 and 347which are adapted to detect the envelopes of output voice signals fromfirst and second microphones 301 and 302, respectively. The circuit alsocomprises an operational amplifier 348 for comparing the output signalsfrom the first and second microphones with each other after theenvelopes of these output signals have been detected. If there is adifference between the output level at the first and second microphones301, 302, the output voltage will be high at the operational amplifier348.

The video camera further includes a gain control circuit 349 forcontrolling the gain at the output of the first microphone 301 with theoutput voltage of the operational amplifier 348. If the operator's voiceoutput signal from the second microphone 302 is high, the output of theoperational amplifier 348 also becomes high. This results in reductionof the output gain of the first microphone 301 such that the operator'svoice will be recorded in a reduced level.

In the fourth embodiment shown in FIG. 5, a video camera utilizes avoice recognizing system 430 which comprises a sound analyzer 431, avoice recognition microcomputer 432 also functioning as a processor, anda dictionary data storage 433, almost all of these parts being in theform of integrated circuit. The voice recognizing system 430 receivesthe output voice signal of the second microphone 402 and is responsiveto any wording emitted from the operator to make an output port "high".For example, if the wording from the operator is "record", "stop","zoom" or "rear-light compensation", each of these wordings is assignedto make the corresponding one of the output ports 1, 2, 3 and 4 of thevoice recognizing system 430 "high". If these output ports are connectedwith the respective input ports of a mode control microcomputer 414 forcontrolling various operations of the one-piece type video camera, asequence controller 412 in the video camera will receive the samesequence signal as generated by actuating any one of various switchesfor "record", "zooming-up" and others from the voice recognizing system480 at each time when the respective one of the above wordings isemitted from the operator. In such a manner, the operational mode in thevideo camera can be controlled by the operator's voice.

Although the previous embodiments have been described as to thereduction of the operator's mode commanding voice, the same structuremay be used to reduce the mechanical oscillating noises from the drivesin the video camera without any adverse affection on recording.

Although the previous embodiments have been described as to only twomicrophones, more than two microphones may be used to improve theaccuracy on recording. Moreover, the second microphone may be in theform of a wired or wireless microphone which is placed remotely from thevideo camera and adapted to perform the remote control of the videocamera with the operator's voice.

FIG. 6 is a block diagram of a circuit used in the fifth embodiment ofthe present invention, which circuit is different from the circuit ofFIG. 5 only in that a delay element 545 is interposed between a secondmicrophone 802 and a frequency filter 880. This delay element 845 hasfunctions and advantages similar to those of the embodiment shown inFIG. 3.

FIG. 7 is a block diagram of a circuit used in the sixth embodiment ofthe present invention, which comprises a voice recognizing system 880,mode control microcomputer 814 and sequence controller 812 all of whichare similar to those of FIG. 5 being added to the third embodiment ofFIG. 4. In addition to the operations described with respect to FIG. 4,thus, the sixth embodiment functions as illustrated in FIG. 5.

FIG. 8 is a block diagram illustrating the seventh embodiment of thepresent invention while FIG. 9 illustrates the circuit and functions ina voice recognizing system used in the seventh embodiment. Referring toFIGS. 8 and 9, the video camera comprises a lens system 713; a two-stagedifferential amplifier 740 for outputting the sum and differencecomponents of output voice signals from first and second microphones701, 702; microphone amplifiers 741 and 742; a band-pass filter 743 andan amplifier 744, all of which are mounted within the body of the videocamera 710.

The operation of the seventh embodiment will be described below.

In the arrangement of FIG. 8, the first microphone 701 has a relativelyhigh sensitivity and a relatively wide-beamed directivity such that avoice can be collected from a subject through a broadened range. On theother hand, the second microphone 702 has a relatively low sensitivityand a narrow-beamed directivity. Thus, the second microphone 702 willnot collect the subject's voice. Voice signal collected through thefirst microphone 701 is amplified by the microphone amplifier 741 andthen applied to the two-stage differential amplifier 740 at itstransistor TR₁. The difference gain of the two-stage differentialamplifier 740 is:

    G.sub.DIP =(R.sub.3 /R.sub.2) (R.sub.6 /2R.sub.5)

and amplified before applied to a recorder 711 in the video camera 710.The voice signal is recorded on a video tape together with an imagesignal from the lens system 713. At the same time, noises from variousdrives such as the drum motor in the recorder 711 and several motors inthe lens system 713 for zooming, focusing, iris drive and others arecollected together through both the first and second microphones 701,702. Thus, these noises are canceled equivalently in the differencecomponent. Only the voice signal from the subject can be recorded on thevideo tape with a good S/N ratio.

Even if any general conversation between the operator and the subject ismade, for example, "move left" or "look this way", it will not berecorded on the video tape since the general conversation is collectedsimultaneously through the first and second microphones 701, 702.

The voice recognizing system 730 in the seventh embodiment will operateas follows:

The dictionary data storage 733 in the voice recognizing system 730 haspreviously store about ten of wordings generally used on controlling thevideo camera, for example, "record", "pause", "zooming-up","zooming-down", "rear light", "stop" and others.

If the operator whispers "record" near the microphone 702 while lookingin the view finder 707, that voice signal is received by the microphone742 and then amplified by the microphone amplifier 742, the amplifiedvoice signal being applied to the two-stage differential amplifier 740at its transistor TR₂. The difference gain of the two-stage differentialamplifier 740 is represented by:

    G.sub.COM =R.sub.4 /R.sub.1 +(R.sub.2 /2).

Thus, the voice signal is amplified by this gain at the amplifier 740before outputted. The sum component is supplied to the voice recognizingsystem 730 through the band-pass filter 743 and the voice amplifier 744,wherein the content of the voice signal is identified.

The voice recognizing system 730 shown in FIG. 9 is a voice recognizingsystem utilizing the composite similarity accumulating process whereinan original sound inputted through the amplifier 744 is transformed intoanalog data through a plurality of channels (seven in FIG. 9) each ofwhich comprises a band pass filter and a full-wave rectifier. The analogdata is converted into digital data through a multiplexer and an A/Dconverter. At a microcomputer 732, the digitized signal data is comparedwith dictionary data including about ten of registered wordings. Ifthere is a wording corresponding to the digitized signal data in thedictionary data, an I/O signal is generated. This sequence signal isapplied to the sequence controller 712 shown in FIG. 8 which in turncontrols the video camera 710 in the commanded mode.

At this time, it is natural that the operator's voice commanding theoperational mode of the video camera is collected slightly by the firstmicrophone 701. However, this is negated at the two-stage differentialamplifier 740. As a result, the operator's command voice signal does notappear in the difference component and will not be recorded on the videotape.

The voice recognizing system utilizing the composite similarityaccumulating process is suitable for use in the voice recognition ofunspecified persons. The present invention is not limited to this typebut may be applied to any other suitable process such as linear matchingprocess or the like. Furthermore, the voice recognizing system may beadapted to recognize only the voice of a specified person so as toimprove the reliability.

It is desirable that the first and second microphones 701, 702 aredisposed at positions in which they are directly opposed to each other.It is further desirable that the second microphone 702 is located nearthe mouth of the operator when he looks in the view finder 707.

Moreover, the second microphone 702 may be of a necktie pin type whichis separated from the video camera body 710.

In such a manner, the recording of the operator's voice can beeliminated or reduced in level by providing a video camera whichcomprises a first microphone for collecting any voice incoming from asubject, a second microphone for collecting any voice emitted from anoperator, an operational amplifier for subtracting the output voicesignal of the second microphone from the output voice signal of thefirst microphone and means for recording the output voice signal of theoperational amplifier on a video tape.

The elimination or reduction of the operator's voice level to berecorded on the video tape may be accomplished similarly by providing avideo camera which in addition to the first and second microphones,comprises an envelope detector for detecting the envelopes of theoutputs of the first and second microphones, an operational amplifierfor comparing the output levels of the first and second microphonesafter passed through the envelope detector, a gain control circuitresponsive to the output of the operational amplifier for changing thegain in the first microphone and means for recording the output signalof the first microphone on a video tape after the output signal has beenregulated in gain by the gain control circuit.

In addition to the aforementioned components, the video camera of thepresent invention comprises a voice recognizing system for recognizingthe content of a mode commanding voice signal collected through thesecond microphone. The voice recognizing system is responsive to therecognized content of the mode commanding voice signal to control theoperational mode of the video camera. Therefore, the video camera willnot require any manipulation by the operator's finger. Thus, theundesirable motion in the video camera can be avoided.

What is claimed is:
 1. A video camera having a controllable opticalsystem receiving an image and converting the image into an image signal,comprising:a first directional microphone directed away from an operatorof the video camera producing a first signal representing soundsreceived thereby; a second directional microphone directed towards theoperator producing a second signal representing sounds received thereby;a voice signal generator, operatively connected to said first and seconddirectional microphones, including a differential amplifier generating afirst voice signal based on a difference between the first signal andthe second signal and a second voice signal based on the sum of thefirst signal and the second signal; a recorder, operatively connected tosaid voice signal generator, recording the first voice signal and theimage signal on a recording medium; a voice recognizer outputting a modecommand signal in response to a successful recognition of the secondvoice signal as a known command; and a controller controlling the videocamera in response to the mode command signal received from said voicerecognizer.
 2. The video camera as defined in claim 1, wherein saidvoice recognizer comprises:plural channels of analog data generatingmeans for filtering and rectifying the second voice signal to generateanalog data; a multiplexer multiplexing the analog data; ananalog/digital converter converting the multiplexed analog data intodigital data; a dictionary data storage device storing known commands;and a microcomputer determining whether or not the digital data is aknown command stored in said dictionary data storage device andoutputting a mode command signal corresponding to the known command. 3.The video camera of claim 1 wherein said controller controls the opticalsystem in response to the mode command signal received from said voicerecognizer.
 4. The video camera of claim 1 wherein said controllercontrols said recorder in response to the mode command signal receivedfrom said voice recognizer.
 5. The video camera of claim 1, wherein saidfirst microphone has a relatively high sensitivity and wide directivity.6. The video camera of claim 1, wherein said second microphone has arelatively low sensitivity and narrow directivity.
 7. The video cameraof claim 1, wherein said first microphone and said second microphone areboth adapted to collect sounds generated by mechanical vibrationscreated within an interior of the video camera.
 8. The video camera ofclaim 1, further comprising a band pass filter, interposed between saidvoice signal generator and said voice recognizer, band pass filteringthe second voice signal.
 9. The video camera of claim 8, furthercomprising an amplifier, interposed between said band pass filter andsaid voice recognizer, amplifying the second voice signal.
 10. A methodfor controlling a video camera having an optical system that receives animage and converts the image into an image signal, comprising the stepsof:producing a first signal representing sounds received from anoperator; producing a second signal representing sounds received from asubject; generating a first voice signal based on a difference betweenthe first signal and the second signal, generating a second voice signalbased on the sum of the first signal and the second signal; recordingthe first voice signal and the image signal on a recording medium;recognizing a known command from the second voice signal and outputtinga corresponding mode command signal in response thereto; and controllingthe video camera in response to the mode command signal.
 11. The methodof claim 10 wherein the controlling step further comprises the step ofcontrolling the optical system in response to the mode command signal.12. The method of claim 10 wherein the controlling step furthercomprises the step of controlling the recording step in response to themode command signal.
 13. The method of claim 10, wherein the recognizingstep further comprises the steps of:filtering and rectifying the secondvoice signal to generate a plurality of channels of analog data;multiplexing the plurality of channels of analog data; converting themultiplexed data into digital data; determining whether or not thedigital data is a known command stored in a dictionary and outputting amode command signal corresponding to the known command upon a successfuldetermination.
 14. The method of claim 13 wherein the determining stepfurther comprises the step of accessing a dictionary storing knowncommands.
 15. The method of claim 10, wherein the steps of producing thefirst signal and the second signal include producing the first andsecond signals which contain sounds generated by mechanical vibrationscreated within an interior of the video camera.
 16. The method of claim10, further comprising the step of band pass filtering the second voicesignal prior to the step of recognizing.
 17. The method of claim 16,further comprising the step of amplifying the second voice signal priorto the step of band pass filtering.